The present invention relates to a superconducting structure, a superconducting device using the above structure, and a superconductive material used in the superconducting device.
A pn junction superconducting device using two superconductors of the p- and n-conductive types has been well known (refer to, for example, JP-A-57-176780 laid open on Oct. 30, 1982). In this prior art, two superconductors are kept indirect contact with each other, to form a superconducting device, and a superconducting tunnel current is generated not by the superconducting proximity effect but by the tunnel effect.
Meanwhile, Cu-oxide superconductors which have hitherto been found, have a crystal structure belonging to perovskite and modified versions thereof. The perovskite structure and the modified versions include the following structures. In the first structure, the octahedral arrangement of oxygen atoms with a copper atom at the center is used as the polyhedron formed of copper and oxygen atoms. In the second structure, one or two oxygen atoms are removed from the octahedral arrangement of oxygen atoms to form a square pyramidal arrangement or square planar arrangement. In the third structure, the octahedral arrangement, square pyramidal arrangement and square planar arrangement are piled. In these structures, when the atomic coordinates of a copper atom are expressed by (0, 0, 0), oxygen atoms are disposed in the vicinity of each of three positions expressed by atomic coordinates (1/2, 0, 0), (0, 1/2, 0), and (0, 0, Z), where Z.noteq.0.
Although the mechanism of superconductivity in Cu-oxide superconductors has not yet been clarified, square planar arrangement of oxygen atoms is two-dimensionally repeated in the crystal structures of Cu-oxide superconductors so as to form a Cu-0 plane. Compounds which can be used as a Cu-oxide superconductor, are described in the following publications:
B. Grande, Hk. Muller - Buschbaum and M. Schweizer, Z. anorg. allg. Chem., 428 (1977) 120. PA0 Hk. Muller-Buschbaum and W. Wollschlager, Z. anorg. allg. Chem., 414 (1975) 76.